In a color filter used for liquid crystal displays, it has been recommended to form black matrix with light-shielding film for filling up the space between pixels to have high-contrast images. Examples of such black matrix generally include the following.
1. Using ink or photosensitizer containing black pigment, black matrix is formed in a portion to be shielded on a transparent substrate.
2. A metal thin film such as chromium is formed on the entire transparent substrate by sputtering or evaporation method, and thereafter resist to shield light is formed by applying photosensitive resist on the metal thin film, exposing through a mask, and developing, and unnecessary portions are removed by etching to form black matrix.
However, the black matrix of the above 1 can suppress reflection of black matrix from the glass surface but the film thickness must be increased in order to achieve satisfactory light shielding effects. When the black matrix is printed with ink, satisfactory film thickness is unable to be obtained and it is difficult to suppress TFT optical leak current. It cannot form fine black matrix, neither. When photosensitizer is used to increase the film thickness, light does not penetrate inside the film which remains unexposed, due to the black color of the photosensitizer. When it is intended to achieve an optical density of 3.5 or higher, the black matrix film is too thick to maintain smoothness and becomes inadequate for assembling liquid crystal panels.
The black matrix of the above 2 is formed by evaporation or sputtering method, but because these have metallic luster, reflection of black matrix when seen from the glass surface is extremely large as 59%, causing the panel contrast to markedly lower. In addition, these forming methods require expensive vacuum equipment, and if optical density exceeding 3.5 is intended to achieve, long-term treatment is required, resulting in extremely poor productivity and high costs.
Consequently, the object of the present invention is to solve the problems described above and to provide glass substrate for liquid crystals with the total reflection ratio of 6% or less by seeing through from the glass surface and optical density of 3.5 or higher as well as color filters for TFT liquid crystals, TFT liquid crystal displays for projection, and color TFT liquid crystal displays using the glass substrate for liquid crystals.